The present invention relates to improvements to a storage medium which increase the storage capacity of the medium. More particularly, the present invention relates to a storage medium in which sector address information is recorded using MSR techniques.
Optical disks are widely used as external storage media for computers. Magneto-optical disks have become popular because they are rewritable and provide a relatively high recording density. In the past, 3.5 inch magneto-optical disks were only capable of storing 128 MB of information. Recent advances, however, have enhanced the storage capacity of 3.5 inch magneto-optical disks to 1.3 GB, and even greater increases in storage capacity are presently being sought.
Magneto-optical disks include at least one recording layer formed on a substrate. Information is recorded/reproduced from magneto-optical disks using a laser light source and a magnetic source. Typically, grooves (tracking guide grooves) are formed in spiral fashion on the substrate of the medium. Data is recorded on tracks provided on lands between these grooves.
In the past, the recording density of magneto-optical disks has been limited by the diameter of the beam spot of the laser beam. However, in recent years, magneto-optical super resolution technology known as MSR (Magnetically Induced Super Resolution) has facilitated the recording and retrieving of a mark smaller than the diameter of a laser beam. For example, with a 3.5 inch magneto-optical disk, recording and retrieving of a mark smaller than the laser beam spot with track pitch of 0.90 xcexcm and a mark length of 0.38 xcexcm is now possible. Consequently, a ten fold increase in storage capacity to 1.3 GB has been realized.
Magneto-optical disks record and retrieve in a storage unit termed a sector. By manner of illustration, FIGS. 12A and 12B show a traditional MSR magneto-optical disk sector format in which sector address information portion 90 is physically formed as an indented (embossed) pit with a stamper in the same manner as a tracking groove. Sector address information 90 includes a sector mark SM which indicates the beginning of a sector, PLL phase lead-in term signal VFO1, address mark AM indicating the beginning of the first sector ID, first sector address ID1, PLL phase lead-in term signal VFO2, address mark AM indicating the beginning of the second sector, second sector address ID2 and post amble PA indicating the end of the sector address information portion.
Sector address information stored in ID1 and ID2 includes track number and sector number information. The second sector address ID2 stores the same information as the first sector address, and is included as a backup in case ID1 becomes unreadable.
A gap 91 separates the sector address information portion 90 from VFO area 92 in which a VFO pattern for adjusting the frequency is recorded. Sync byte area 93 is interposed between a data area 94, and the aforementioned VFO area 92. A post amble (PA) 95 and buffer 96 for a buffering area are formed subsequent the data area 94.
Data is recorded at a high density in the data area 94 portion using MSR techniques. In contrast, sector address information portion 90 is recorded at a significantly lower density than the data recorded in the data portion 94, since it is physically formed by embossing or the like.
Accordingly, one problem associated with conventional magneto-optical storage mediums relates to the relatively large area required to store sector address information, and the ensuant decrease in usable storage capacity of the medium.
One object of the present invention is to increase the usable storage capacity of a magneto-optical storage medium by reducing the area required to store sector address information.
Another object of the invention is provide a storage medium including an error correction code for correcting a sector address.
Another object of the invention is to provide an improved method for determining whether a head is in an off track condition during a read operation.
Yet another object of the invention is to provide an improved method for verifying that a write operation has written to the correct sector, where the target sector is not read prior to the writing operation.
Briefly, the present invention relates to an improved storage medium for storing information. Information is stored on a plurality of tracks formed on the storage medium, each of the tracks being divided into a plurality of sectors. Each sector includes a physically formed sector beginning identifier provided at a leading portion of the sector, and an information storing portion. At least one sector address portion for storing a sector address is provided at a leading end of the information storing portion, and a data portion for storing user data is provided after the sector address portion.
These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings.